Coating material for metal articles



Patented Apr. 26, 1932 tJNlTED STATES PATENT OFFICE RUDOLF AUERBAGH, F BERLIN-NEUENHAGEN, GERMANY, ASSIGNOB T0 WILHELM STEINHORS' I, 0F LEIPZIG, GERMANY COATING MATERIAL FOR METAL ARTICLES No Drawing. Application filed April 5, 1929, Serial No. 352,920, and in Germany April 7, 1928.

My invention relates to alloys of metals for coating iron and steel articles such as steel wire, rods, plates, sheet iron etc.

The object'of the invention is to provide 5, an alloy which on being applied to the articles concerned so as to form a coating will render said articles absolutely safe against corroding attacks e. g..by moisture such as Wet, salty sea air, acidiferous vapours etc. Another objectof the invention is to prepare a metal alloy for the purpose concerned, which on being applied in molten state to the articles concerned will form on the latter a smooth surface which by reason of its being free from fissures, cracks etc. will lastihgly preserve its anticorroding qualities ven under the most adverse atmospheric conditions.

As the result of extended comparative experiments of mine trying to find out the technically and economically best alloys for the purpose concerned, alloys of zinc containing about 70% zinc and 30% cadmium have proved to be most advantageous for coating iron and steel articles.

I am aware that as far back as in 1849 it has been proposed in patent literature to use cadmium alloyed with zinc in the proportion of abut 400 parts cadmium to 150 parts of zinc for coating iron and other metals.

However I have found in the course of my experiments that alloys in which cadmium predominates are not fit in practice for coating purposes because by a rather rapid oxidation of the molten cadmium alloy foamy slags are produced which will adhere on the l articles on being dipped into and removed i from the molten bath, producing on the former a rough surface full of fissures and cleavage cracks; by reason of said fissures and cracks the coated surfaces are subject to rapid destruction by adverse atmospheric conditions such as cold weather during which Water having penetrated into said fissures will freeze and will by bursting the coat very effectively destroy the latter.

Moreover the relati ely high cost of cadmium curtails its utilization for coating purposes in the form of alloys containing a predominating percentage of cadmium, and it may be due to both the above specified drawbacks that cadmium alloys altogether have not come into general use heretofore although attention to their anticorrosive qualities has been drawn by a former inventor as far back as in 1849.

The said drawbacks have been eventually overcome by this invention according to which a zinc alloy containing only about 30% of cadmium is used as coating substances for iron and steel articles.

Various changes and modifications may be made and may suggest themselves to those skilled in the art of preparing anticorrosive alloys, without departing from the spirit of my 1nvention:

Although according to my experiments the specified percentage parts of zinc to 30 parts of cadmium has given the best results both from a technical and an economical point of view, the cadmium content may be varied within close limits and other metals of suitable nature such as tin may be added to advantage in relatively small quantities.

What I claim is:

An anticorrosive alloy to be used in molten state for coating iron and steel articles which consists of zinc and cadmium alloyed in the proportion of about 70% zinc to 30% cadmium.

RUDOLF AUERBACH. 

